The corrosion of machine components in the presence of moisture and other corrosive substances is an important cause of mechanical system failures. One of the widely used means of controlling or preventing this corrosion is to employ the corrosion preventing properties of the lubricants, fuels, and functional fluids (for example, hydraulic brake fluids) used in the system. The rust preventing properties of lubricants, fuels and functional fluids can be enhanced by the addition of chemical additives. In order to determine the performance of these fluids in preventing the corrosion of machine elements a wide number of tests have been devised and have been used by industry. Some of the most widely used tests are described hereinbelow.
The Humidity Cabinet Test (ASTM D-1748) evaluates the ability of the test lubricant or other coating to protect a specially prepared steel specimen from rusting when stored in a chamber at an elevated temperature in air substantially saturated with water vapor.
The Turbine Oil Rust Test (ASTM D-6665) evaluates the corrosion characteristics of a fluid on a cylindrical steel sample while the sample is submerged in a constantly stirred mixture of the test fluid in water.
The Test for Corrosiveness and Oxidation Stability of Light Oils (Federal Test Method 5308) evaluates the corrosion of coupons of several metals while immersed in a sample of oil which is heated and aerated continuously.
The Test for Corrosion of Lead by Lubricating Oils (Federal Test Method 5321) employs the immersion of lead samples in the presence of a copper catalyst in heated test oil with continuous aeration in order to determine corrosion protection performance.
These and several other similar methods measure the ability of the test oil to prevent corrosion in either a totally liquid or totally vapor phase environment. None of the foregoing tests, however, have proven to produce results or data which correlate with the test which is generally accepted as the standard within the industry for measuring the corrosion protection performance of automotive gear lubricants (The Coordinating Research Counsel L-33 Moisture Corrosion Test).
The CRC L-33 Test is a method for measuring the moisture corrosion protection of lubricating oils which is both time-consuming (about 7 days) and physically cumbersome to perform (the entire automotive rear axle is employed in carrying out the testing procedure). Thus, there is a need in the lubricating materials art for a test procedure which may be expeditiously performed, which utilizes small test specimens and small amounts of test fluids, and which furthermore correlates to the CRC L-33 moisture corrosion test.